Field of the Invention
The present invention relates to an analytical cell suitable for use, e.g., in an analysis of electrode reactions, etc. using analytical equipment.
Description of the Related Art
As is well known, in an electric cell, a negative electrode active material and a positive electrode active material undergo electrode reactions in a charge-discharge process. In recent years, attempts have been made to analyze such electrode reactions during the charging/discharging process using analytical equipment. For example, an analytical cell that can be observed using a transmission electron microscope (TEM) has been proposed in In-situ Electron Microscopy of Electrical Energy Storage Materials (Annual Merit Review, DOE Vehicle Technologies Program, Washington, D.C., May 9-13, 2011).
This analytical cell contains a pair of substrates (silicon substrates). Each of the substrates has a rectangular observation window having a size of about 50 μm×100 μm. The pair of substrates are partially overlapped with each other to form an overlapping portion. In the overlapping portion, the substrates are spaced from each other by a predetermined distance by a spacer interposed between the substrates. The substrates are positioned in a manner that the observation windows face each other. Further, a negative electrode active material in the form of a highly oriented graphite membrane and a positive electrode active material in the form of a LiCoO2 membrane are deposited on one of the silicon substrates by an ion beam deposition method, such that the negative electrode active material and the positive electrode active material are located between the observation windows. It should be noted that each of the negative electrode active material and the positive electrode active material is extracted from a bulk body using a focused ion beam (FIB).
The negative electrode active material and the positive electrode active material are electrically connected to a negative electrode collector and a positive electrode collector (hereinafter also referred to as the “collector”, collectively), respectively, inside the overlapping portion. Each of the collectors extends from the inside of the overlapping portion, such that one end side of each collector is exposed to the outside. Therefore, the negative electrode active material and the positive electrode active material can be electrically connected to the charging/discharging devices, etc. outside the overlapping portion through the collectors.
This analytical cell is observed using a transmission electron microscope (TEM), whereby it is possible to analyze the electrode reactions, etc. in the negative electrode active material and the positive electrode active material. Specifically, firstly, the analytical cell is accommodated in a front end of a holder having a flow channel for electrolytic solution inside the overlapping portion. Then, the electrolytic solution is made to flow through the flow channel of the holder into the overlapping portion, and the collectors are electrically connected to a charge-discharge tester or the like. Consequently, since the analytical cell forms a lithium ion cell, it is possible to cause electrode reactions in the negative electrode active material and the positive electrode active material. At this time, an electron beam is transmitted through the observation window for carrying out the TEM observation. In this manner, it is possible to perform the analysis of the above electrode reactions.